Questions tagged [rf]
Short for Radio-Frequency. Frequencies at which radiation (intentional or not) plays a role. Typically associated with wireless communications, but also relevant for high-speed PCB design.
2,915
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What's the relationship between bandwidth and symbol rate for a modulated signal?
I was hoping somebody could help me with understanding the relationship between the bandwidth of a modulated carrier signal (say using QPSK) and the symbol rate(s) you can transmit across a channel. ...
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1answer
61 views
Small wireless transmitter and receiver [closed]
I am looking for suggestions for wireless transmitter/receiver chips/circuitry. I have the following system in mind:
Multiple transmitters to one receiver
Transmitters do not have access to ...
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2answers
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Accommodating Gain Elements in PLL Loop
Background
I'm working on a PLL based frequency synthesizer for the 20m amateur radio band. For reference, I've asked questions in relation to this project before (see here). It uses the idea of an ...
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1answer
57 views
Antenna ground and digital ground
I know that there are many similar topics here, but none of them answers my questions.
I have an 868MHz RF module (cc1120 + cc1190), the output power is around 27dBm. The module is with a castellated ...
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2answers
472 views
What makes RF transmission so efficient?
I'm a layman in this field. I have a question about RF transmission.
How does the data transferred by RF waves (for example in mobiles, wifi) reach the users accurately in spite of losses during ...
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37 views
How do I find the right MOSFET for my class E amplifier?
I'm trying to build a class E power amplifier for my Tesla coil right now.
The operating frequency is 4MHz, Vcc is 50V and the output power should be around 100W.
I've used Sokal's QEX article to ...
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27 views
What happens if you connect a “slant 45 radio unit” to a linear parabolic antenna?
If I understand it correctly the only difference between linear polarization and slant polarization is that slant polarization is just a 45-degree rotated version of linear polarization, and that ...
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2answers
50 views
low-cost transmitter and receiver, no MCU involved hopefully
a newbie on electronics here.
I would like to create a simple RF kit. on transmitter side, only 1 button. on receiver side, if a valid code is received, a relay activates to provide 12VDC to a load.
i ...
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67 views
Circuit for RF Splitter [closed]
Does anyone know of any resources which describe how to design an RF Splitter circuit with one RF input and multiple (at least 6) RF outputs, whereby the signal strength of each output matches (does ...
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1answer
85 views
Why is a microstrip line unbalanced?
It is known that a coaxial cable needs a balun to provide an optimal supply of a dipole antenna, because of the common mode current that comes back to the transmitter through the external surface of ...
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1answer
30 views
Question regarding Connector
Can someone please help me to understand what type of connector is the below :
How do we classify this 99S12D-40MA5-y connector which is on page 33 in the Catalog document?
Do we call it as a ...
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26 views
AWR, filters saw parameters [closed]
I need files with saw parameters filters (Taiyo Yuden F6KA2G535L4AM-Z) in s2p format for awr. I havent found them on publisher site, where can i find them?
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A low latency wireless communication link
At this moment I'm working on a wireless charging system where feebback (error for PI controllers) is being send by the nrf24l01 modules. I have implemented 2kHz communication link.
Can anyone suggest ...
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1answer
27 views
Estimating Safe Pulsed RF Power given Continuous Wave Power Rating
For a university project I am designing a RADAR transmit/receive module at 9.4 GHz. Right now I'm working on an input power limiter to protect an LNA, but my colleague designing the LNA quotes its ...
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21 views
Kicad Footprint Validation Conflict
I am trying to create a simple SMA connector footprint in Kicad but whenever I try to save the footprint to a library, Kicad generates a "validation conflict" error. I have no visibility ...
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1answer
67 views
Drawbacks of RF downconverting?
I see a lot of RF systems use downconverting schemes in signal reception, like the LNBs for Ku-band TV signals. From what I read, digital downconverters do not harm the signal in the sense that no ...
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55 views
Are magnetic/electromagnetic damp proof courses a scam (active/passive EM Fields to stop capillary water wicking in stone) [closed]
At a home building show earlier this year, there was a company offering "magnetic damp proof course" which sounded a bit like snake oil to me. They pitch it as the next evolution of electro-...
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3answers
170 views
Why is a coaxial cable unbalanced?
Let's consider a coaxial cable which supplies a dipole antenna. My reference for all my statements is here.
My reference says:
Note that the current along a transmission line should be of equal ...
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3answers
528 views
Using a miniature BNC connector on a PCB to measure high-frequency content with an oscilloscope
I am a power electronics engineer in R&D and often measure fast switching waveforms, specifically high bandwidth MOSFET gate signals. When connecting oscilloscope probes in the past I have found ...
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34 views
Rf/voltage powermeter
I want to start a project and i'm clueless even after reading a lot.
I have an rf route with some rf components/equipments connected, analog signals going through (wired). My goal is to check the dB ...
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1answer
78 views
What's wrong with my diode SPICE model for the HSMS-2860?
To be brief, I am as new as they get to creating SPICE models for components so I'm walking blind.
I was trying to create a SPICE model for the HSMS-2860 diode.
HSMS-2860 Schottky Diode Datasheet
Here ...
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1answer
93 views
What is this symbol called? A blue rectangle with a red dot
This is a rectifier circuit in RF Energy Harvesting. I have no idea what does the blue rectangle symbol called. (Found in https://pdfs.semanticscholar.org/d6fe/47f5539a231dfeeef67166977893070788f2.pdf)...
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1answer
67 views
Why aren't magnetic substrates so used for RF printed circuits?
I've recently started working in microwave field, so I don't have big knowledge except for basic theory.
What I've noticed is that, in rf and microwaves printed circuits (for instance for microstrip ...
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1answer
65 views
Difference between a frequency synthesizer and a frequency mixer
I have tried looking a couple different places but cannot find a concise explanation on the difference between a frequency synthesizer and a frequency mixer. My goal is to take a signal at 915 MHz and ...
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1answer
67 views
Radio Frequency Regulations for continuous low-power single-frequency signal
I am somewhat confused about the regulations on the radio frequencies.
I am designing a system using an antenna, which is not used for communications. It is used for sensing based on the reflection ...
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1answer
52 views
Why Does a Shunt Cap Help For Deglitching Digital Signals?
In some of my projects I have digital pulse signals that are sent over fairly long wires (~12in). For example tachometer readings or stepper signals.
I've tried various things to reduce glitches in ...
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2answers
380 views
Reading an Old Philips Radio Manual with SCR rows
I've been looking at the manual for the Philips L4X26T radio and I have noticed that for each of the diagrams, there is a rather peculiar table with three rows of numbers labelled "S", "...
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1answer
89 views
What is the meaning of Directivity and Reflection coefficient for a RX antenna? [closed]
it's known that the circuital models of TX and RX antennas are the following ones:
They are fine, but I find it hard to understand the meaning of some concepts when applied at the RX case. For ...
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0answers
18 views
How to determine patch antenna slit/truncation size for RHCP?
I am designing a patch antenna for a project. It is running at 2.45GHz. I am looking into both rectangular and triangular designs. I need to have a single coaxial feed point. I found all the formulas ...
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62 views
Connect headset to radio
I would like to connect a headset to my radio (Cobra AM845.)
The Cobra radio has a 2,5mm audio jack and the headset has a 3,5mm audio jack. I made a PCB to connect the together as:
When I close ...
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0answers
63 views
Multiple Direct Digital Synthesizers (DDS) to Increase Sample Rate
I’m looking to generate a RF signal sampled at around 10 GSPS operating above the 3GHz mark. In order to maximize data throughput, the signal will be modulated at that frequency (rather than mixing in ...
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What is the purpose of a superstrate above a printed antenna?
I've seen that there are some planar antennas which are not simply a metal patch above a substrate, but present also a dielectric superstrate.
Some examples of this configurations are:
This planar ...
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1answer
26 views
Is spatial multiplexing always required to define MIMO?
From Wikipedia:
In radio, multiple-input and multiple-output, or MIMO (/ˈmaɪmoʊ, ˈmiːmoʊ/), is a method for multiplying the capacity of a radio link using multiple transmission and receiving antennas ...
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1answer
41 views
How to add remote testpoints to non-multidrop RS422 without causing reflections?
I have a RS422 non-multidrop connection between two connectors on a PCB (CLK+/- and DATA+/-) clocked at 1MHz, and currently routed with adapted edge-coupled microstrips (120Ohm differential impedance)....
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1answer
26 views
Can i Increase the NFC range upto 50cm by making a bigger antenna? i only want to write data into a NFC enabled EEPROM?
As NFC are active upto 15cm range, i/m using a PN532 to write data into a NXP NFC enabled EEprom, which is successful, i want to increase its range by 2X by increasing the Power or size of Antenna for ...
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Anything obviously suboptimal about this design?
RF novice here, this is the first PCB I've designed and I'm just wondering if anyone more experienced than I (which is most people) sees anything glaringly wrong/bad/in need of improvement with this ...
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1answer
43 views
Suppression of current in the ground plane
I’m designing an antenna with two polarisation. The stripline from the two polarisation are close in one layer therefore the isolation between the two pol is degraded because of some current flowing ...
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Bode Fano criterium and low Q-factor
I am currently studying the Bode-Fano criterium and how it can be used to design wideband amplifiers.
It's stated that a low load Q-factor (high resistive component with respect to the imaginary one) ...
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1answer
178 views
What is this structure on an RF PCB?
I'm looking at a picture of an RF PCB meant to operate at a few GHz, and I'm having trouble understanding exactly what this is:
Obviously there are some transmission lines, and something that looks ...
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2answers
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What kind of structure is this small GSM antenna?
Two of these types of antennas comes with the ADALM-PLUTO SDR evaluation kit.
According to this page, they should be JCG401 antennas for the 900 and 1800 GSM bands, but the datasheet does not tell ...
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8answers
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In which direction do electric signals flow?
We know that electrons move from the negative to positive terminal, and that holes flow in the conventional direction of current - from the positive to negative terminal.
I've always assumed that this ...
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1answer
53 views
433 MHz Transceiver - understanding OOK demodulator parameter 'OokFixedThreshold'
I would appreciate some help to understand a parameter for this device https://www.semtech.com/products/wireless-rf/fsk-transceivers/sx1231h. I'm far from an expert at RF matters and this question has ...
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1answer
43 views
What does SWR and reflected power mean in terms of power actually dissipated in a load?
I'm struggling to understand the "meaning" of VSWR in the context of power delivered to a load.
Say I have a transmitter operating at 10MHz, a short (~1m) piece of assumed-lossless ...
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2answers
56 views
Are distributed element filters really distributed?
When looking at distributed filters etched into PCB, I have a hard time understanding why they called distributed. Most of them can be broken into sections and have basically a 1 to 1 correspondence ...
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1answer
51 views
ADS Simulation of IV Diode Characteristics
I’m still quite new to ADS, and I’m trying to get a simple simulation of the IV diode characteristics.
I want to plot the diode current against a DC sweep from -0.2V to +0.2V
Here’s what I’ve got so ...
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3answers
654 views
How does someone design a low frequency FM radio transmitter?
I'm relatively new to the topic but I'm intending to transmit some data from a measurement system in a cave to a receiver on the surface. I understand that I can use a SDR (software defined radio) to ...
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Design of a low frequency (80 kHz) voltage-controlled oscillator circuit
I'm working on a project involving low frequency, through-the-earth data transmission from a transmitter in a karst cave system to a receiver on the surface. I've worked out that a SDR can be used for ...
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2answers
37 views
ADS Simulation of Half-Wave Rectifier
I’m trying to simulate a half wave rectifier for a -84dBm 2.4GHz AC signal.
The rectifier doesn’t seem to be giving me the correct waveform - the negative half cycle isn’t blocked?
Also sort of ...
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0answers
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Single balanced mixer, multi-tone analysis
I realized the circuit shown below on ADS.
Schematic of the mixer can be shown below.
As can be clearly seen from the figure below, to perform a multi-tone analysis RF signal is feeded with two ...
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2answers
52 views
How to calculate impedance of a PCB trace Antenna in Altium w.r.t. a given frequency?
I am keeping things abstract as I intend to learn and not just copy another design.
So, suppose I am trying to design an antenna of impedance Z and frequency f.
Now, in Altium 18, there is a feature ...
